Category: Biomedical Measurements
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Commonly used EEG Electrodes
The most commonly employed electrodes for recording electroencephalographic signals from the brain (EEG) are cup electrodes and subdermal needle electrodes. Cup electrodes are fabricated from platinum or tin approximately 5-10 mm in diameter. These cup electrodes are filled with a conducting electrolyte gel and can be attached to the scalp with adhesive tape. Recording of…
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The Principles of Microbial Biosensors
Introduction The underlying basis of a microbial biosensor is the close proximity between an immobilized microorganism that serves as a specific recognition element and an electrochemical or optical sensing transducer that is used to convert the biochemical signal into an electronic signal that can be processed. The manufacture of a microbial biosensor requires the immobilization…
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The Instrumentation for Recording ECG Signals
Since the electrical events in the normal heart precede its mechanical function, ECG signals play an important role in diagnosis and monitoring of a wide variety of cardiac abnormalities including myocardial infarction and chamber enlargements. Hence, ECG signal acquisition systems are extensively employed in cardiology, cardiac catheterization laboratories, intensive and cardiac care units, etc. The…
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The Measurement of Tissue Optical Properties
The measurement of optical properties i.e. absorption coefficient (μa), scattering coefficient (μs), and scattering anisotropy (g) of biological tissues is a key challenge in the field of biomedical optics. Information about these parameters is essential in both therapeutic and diagnostic applications of light in medicine. Case in point, optical properties are needed to predict fluence…
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The Operation of Fiber-optic Based Blood Gas Sensors
To perform in vivo measurements and to steadfastly analyze blood gases, a small, stable, accurate and bio-compatible sensor is needed that can be inserted in the blood flow of an artery through an arterial cannula and remain in place for several days. Additional, it has to be low cost so that it could be used…
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The Principle of Surface Plasmon Resonance Sensors for Detection of Antibody & Antigen Interactions
When monochromatic polarized light for instance, from a laser source impinges on a transparent medium having a conducting metallized surface (e.g. Ag or Au), there is a charge density oscillation at the interface. When a light at an appropriate wavelength interacts with the dielectric-metal interface at a defined angle, called the resonance angle, there is…
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Key Properties of Bioelectrodes
To record biopotentials, an interface is required between the electron-conducting copper wires connected to signal conditioning amplifiers and the ion-conducting environment of living organisms. Electrodes form this interface. Some of the several kinds of electrodes are better than others in terms of low noise and ease of use. Initial ECG electrodes were non-disposable, nickel-silver plated…
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The Principle of Temporal Artery Thermometer
This is a non-invasive scanning thermometer for measuring core body temperature. The measurement is based on scanning the area above the temporal artery using an IR detector. The superficial temporal artery extends directly from the external carotid artery and travels in front of the ear. Anatomically, it is lying approximately 1 mm below the skin,…
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Basic Features of Enzyme Based Biosensors
Enzymes are the commonly used biological sensing element in the fabrication of various biosensors. Enzymes have unique properties and ability to accelerate chemical reactions inside biological cells. Most enzymes react only with specific substrates even though they may be contained in a complicated mixture with other substances. However, it is imperative to keep in mind,…
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Fleisch Pneumotachometer Operation & Biomedical Application
Fleisch Pneumotachometer is one of the most common types of airflow transducers. It consists of a straight short-tube with a fixed screen obstruction in the middle that produces a slight pressure drop as the air is passed through the tube. The pressure drop created across the screen is measured by a differential pressure transducer. The…